Acoustic Guitar Body Types
The most significant change in guitar body design came in the 1920s, when guitars were designed to accept steel strings, rather than the traditional gut (or later nylon) strings.
Martin Guitars
Martin Guitars, a company with a long history of building these instruments, began giving numerical codes to the various size bodies.
Smaller-bodied 12-fret guitars included the models 0, 1, and 2, while the 14-fret instruments included the 00 and 000 models. The 000 style is favored by players who want a brighter, cleaner sound, while still having a full-sized body. As an example, the Eric Clapton Signature model is a 000 size guitar.
Meanwhile, for those who wanted an acoustic with a richer bass response, Martin began building the so-called "dreadnought" models, which (trivia fans take note) were named after a famous British battleship. Many of Martin's most popular designs have been the D-sized instruments, from the relatively plain D-18 to the top-of-the-line D-45, with its ornate inlays.
Gibson Guitars
Not to be outdone, Gibson introduced their jumbo "flat-tops" - guitars like the J-45, the J-160E (as used by the Beatles), and the "Super Jumbo J-200," the company's "King of theFlat-Top Guitars."
From there, various manufacturers used these basic shapes and sizes as jumping-off points for other designs that included both sharp and rounded cutaways on the treble bout, as well as the unusual (but effective) Ovation guitars with their Lyrachord bowl-back designs.